In recent years, an organic electroluminescent element (hereinafter, referred to as an organic EL element) using an organic material has been regarded as promising, for example, in applications such as an inexpensive large-area full-color display device of a solid-state light-emitting type and a light-emitting element of a writing light source array, and the research and development of organic EL elements have been actively promoted.
The organic EL element is, generally, a thin film-type element that is provided with a substrate, a first electrode, an organic compound layer including a light-emitting layer, and a second electrode, and is a thin film-type element in which the first electrode, the organic compound layer and the second electrode are formed on the substrate in this order. Meanwhile, one of the first electrode and the second electrode constitutes an anode and the other constitutes a cathode. In addition, the light-emitting layer is constituted of one or a plurality of organic layers containing an organic light-emitting material.
In the organic EL element having such a configuration, when a voltage is applied between the first electrode and the second electrode, holes are injected into the light-emitting layer from one electrode (anode) and electrons are injected into the light-emitting layer from the other electrode (cathode). Then, the hole and the electron injected in the light-emitting layer recombine in the light-emitting layer, and thus the energy level of the organic light-emitting material returns from the conduction band to the valence band. The energy generated at this time is released as light from the light-emitting layer.
In the organic EL element that emits light based on the above-mentioned principle, a non light-emitting point called a dark spot expands over time in the light-emitting surface. The expansion phenomenon of the dark spot is generated due to the deterioration of the electrode, organic layer (light-emitting layer) or the like of the organic EL element, by permeation of oxygen or water vapor from the outside. Therefore, in order to prevent such permeation of oxygen or water vapor into the organic EL element, conventionally, various sealing technologies of the organic EL element are proposed (for example, see Patent Literatures 1 and 2).
In Patent Literature 1, a technique of providing a sealing film on an element substrate of an organic EL element is proposed. Furthermore, in Patent Literature 2, a technique of forming an inorganic sealing film on an element substrate of an organic EL element, and furthermore, sticking a sealing member on the inorganic sealing film via a sealing member is proposed.